A Bag Implementation That Links Data - Data Structures and Abstractions with Java - page 77

{

next = nextNode;
} // end setNextNode
} // end Node

3.28

The class LinkedBag can access Node , as just given in Listing 3-5, if both classes are in the same
package and we modify LinkedBag slightly. Each occurrence of Node within LinkedBag must now
appear as Node<T> . We begin to make these changes to LinkedBag and highlight them in Listing 3-6.

LISTING 3-6

The class LinkedBag when Node is in the same package

package BagPackage;
public class LinkedBag<T> implements BagInterface<T>
{

private Node<T> firstNode;
. . .

public boolean add(T newEntry)
{

Node<T> newNode = new Node<T>(newEntry);
newNode.setNextNode(firstNode);
firstNode = newNode;
numberOfEntries++;

return true ;
} // end add
. . .
} // end LinkedBag

Project 3 at the end of this chapter asks you to complete this revision of LinkedBag .

3.29

As an inner class with a declared generic type. The version of LinkedBag just described in
Listing 3-6 could define Node as an inner class. Node would be similar to the class given in
Listing 3-5, but would require the following changes:

• Omit the package statement.

•

Make the class, constructors, and methods private.

•

Replace the generic type T with another identifier, such as S .

Since both LinkedBag and Node declare generic types, they must use different identifiers to repre-
sent them.
Project 4 at the end of the chapter asks you to revise Node and LinkedBag as described here.

The Pros and Cons of Using a Chain to Implement the ADT Bag

3.30

You have seen how to use a chain in the implementation of the ADT bag. One of the greatest
advantages of this approach is that the chain, and therefore the bag, can grow and shrink in size as
necessary. As long as memory is available, you can add as many nodes to a chain as you wish.